122 BOTANICAL GAZETTE [FEBRUARY 
Cornus canadensis, Clintonia borealis, Mitella nuda; and such bog 
forms as Andromeda glaucophylla, Ledum groenlandicum, Aspidium 
Thelypteris, and Drosera rotundifolia. Aside from these incidental 
occurrences, there is a group of species that inhabit crevices on the 
shores everywhere and which are rarely found in other habitats. 
By far the most important of the early arrivals on account of its 
abundance and densely tufted growth is Potentilla tridentata Ait. 
(three-toothed cinquefoil) (fig. 19). Other noteworthy pioneers 
are Campanula rotundifolia L. (bluebell), Solidago hispida Muhl. 
(goldenrod), Achillea Millefolium L. (yarrow), Aster ptarmicoides 
Tr. , Saxifraga tricuspidata Rottb. (three-toothed saxifrage), 
Deschomssic caespitosa (L.) Beauv. (hair grass), Trisetum spicatum 
(L.) Richter. Another group of plants deserves mention. These 
inhabit moist sheltered crevices and are also characteristic of the 
margins of rock pools. They are Primula mistassinica Michx., 
Pinguicula vulgaris L. (butterwort), Selaginella selaginoides (L.) 
Link, Lycopodium Selago L., Polygonum viviparum L. (alpine buck- 
wheat), Tofieldia palustris Huds. (false asphodel), T. glutinosa 
(Michx.) Pers., Parnassia palustris L. (grass of Parnassus), P 
parviflora DC, Carex atrata L. var. ovata (Rudge) Boott, C. bicolor 
All., C. Halleri Gunn., C. paupercula Michx. var. pallens Fernald, 
Allium Schoenoprasum L. var. sibiricum (L.) Hartm., Empetrum 
nigrum L. (crowberry), Euphrasia arctica Lange (eyebright), 
Prenanthes racemosa Michx. (rattlesnake root), Calamagrostis 
hyperborea Lange. Especially characteristic of moist cliffs are 
the mosses Swartzia montana (Lamk.) Lindb., Tortula ruralis (L-) 
Ehth., Encalypta procera Bruch, E. ciliata (Hedw.) Hoffm. The 
result of occupation by these classes of plants is the accumulation 
of humus, with the accompanying decomposition of the adjacent 
rock. 
With these plants, or usually somewhat later, come in certain 
low shrubs, among them two blueberries (Vaccinium uliginosum 
L. and V. pennsyloanicum Lam.). More important than these, 
in fact most important of all the crevice plants, are the trailing 
shrubs, the two junipers (Juniperus horizontalis Moench and J. 
communis L. var. depressa Pursh) and the bearberry (Arctostaphylos 
Uva-ursi (L.) Spreng.). With them should be included, although it 
